1. Technical Field
The present invention generally relates to semiconductor devices and methods of fabricating the same. More particularly, the present invention relates to fabricating shaped semiconductor structures on fins of FinFETs, and selectively separating the shaped structures from the channel area of the fins.
2. Background Information
In microelectronic integrated circuit fabrication, the bulk silicon wafers where the active regions in the devices are kept in contact with the substrates, have several disadvantages such as increased leakage current and junction capacitance, increased short-channel effects, reduced resistance to effects of radiation and heat. So, in order to overcome these issues and improve the device performance, silicon-on-nothing (SON) devices have been fabricated such that the thin silicon layer is separated from the substrate by an extended void plane or air-gap. In a typical SON process, a silicon germanium (SiGe) layer is deposited on a semiconductor wafer surface by selective epitaxial growth, a silicon bridge is formed above the silicon germanium layer, and then the silicon germanium layer is selectively etched away, leaving an air gap.
To further improve the device performance, silicon-on-replacement-insulator (SRI) devices have been fabricated where the entire transistor is built above the air gap with adjacent silicon areas anchored to the bulk substrate. The air-gap, as formed similarly as SON by SiGe deposition and later etched away, is further filled with conformal oxide to complete the silicon-on-replacement-insulator (SRI) technology. However, it has not been practical to extend the silicon-on-nothing (SON) and silicon-on-replacement-insulator (SRI) processes to develop a semiconductor device utilizing a silicon germanium-on-nothing (SiGeON) or silicon germanium-on-oxide technology to further improve the device performance.
Thus there is a need to improve a method to fabricate a semiconductor device utilizing silicon germanium-on-nothing or silicon germanium-on-oxide technology.